Method to Prepare Lab-Sized Hollow Fiber Modules for Gas Separation Testing

Abstract

The objective in this work was to verify an in-house developed hollow fiber potting procedure for the making of lab modules. The method is a 3-step vertical molding procedure that protects the fiber ends during the fabrication, and which enables hard potting materials to be used for the application of the module at high pressures. (1) The hollow fiber ends are protected with a biopolymeric gel in a mold. (2) A potting material is injected above the gel and solidifies in the voids between the hollow fibers. (3) The gel is removed so the free fibers can easily be cut open.The assembled lab-sized modules were packed with prepared Polysulfone (PSf) hollow fibers (5% and 20% packing densities). The fibers were made by dry–wet spinning from a PSf/NMP/water system and spinning variables adjusted to produce support fibers for coating. The modules were pressurized with N2 up to 10 bar and found to be leak-free. The CO2 permeance at 2, 4, and 6 bar at room temperature was measured to be 44.2 ± 0.3 m3(STP)/(m2·bar·h) for the 5% packing density module and 216.6 ± 0.009 m3(STP)/(m2·bar·h) for the 20% packing density module. The CO2/N2 gas selectivity was 0.79 ± 0.03, which indicated Knudsen diffusion for these support fibers. A multivariate analysis revealed that gelatin was a better protecting gel than calcium-cross-linked sodium alginate. However, the module fabrication had to be done at 2 °C to prevent the gel from melting due to the reaction heat produced from the potting material. About 97 ± 2% of the hollow fibers were preserved by this method.